TN, IPS, VA and ADS are several modes of liquid crystal display. ADS is the abbreviation for Advanced Super Dimension Switch (ADSDS), i.e., an advanced super dimension switch technology, in which a multi-dimensional electric field is formed by an electric field produced at edges of slit electrodes on a same plane and an electric field produced between a layer of the slit electrodes and a layer of a plate-like electrode, and allows liquid crystal molecules in all orientations in a liquid crystal cell, which are located directly above the electrode and between the slit electrodes, to be rotated, thereby enhancing the work efficiency of liquid crystals and increasing the transmissive efficiency. The Advanced Super Dimensional Switch technology can improve the picture quality of TFT products, and has advantages of high resolution, high transmittance, low power consumption, wide viewing angle, high aperature ratio, low chromatic aberration, and push Mura-free, etc.
In manufacturing an array substrate of a TFT liquid crystal display in an ADS mode, the first layer is a transparent pixel electrode layer (usually indium tin oxide (ITO)), i.e., the above plate-like electrode; subsequently, a gate metal layer, a source-drain metal electrode layer and a second pixel electrode layer (usually also ITO) are formed in sequence, and the second pixel electrode layer is the above slit-like electrode. For the sake of illustrative convenience, a plurality of strip-like structures with a certain width and interval in the second pixel electrode layer are called as strip-like pixel electrodes. These strip-like structures and openings between the strip-like structures form the slit-like electrodes.
The TFT pixel structure in the ADS mode has ever been in evolving. An early stage structure was a single domain structure, as shown in FIG. 1. The single domain pixel structure comprises: a gate line 102, a data line 103, a second pixel electrode layer 101, and strip-like pixel electrodes 101a located on the second pixel electrode layer 101 and openings 101b of the second pixel electrode layer. The gate line 102 and the data line 103 intersect each other to define a sub-pixel unit. The data line 103 is connected to a drain electrode 103a of a TFT, and a source electrode 103b of the TFT is connected to the second pixel electrode layer 101. Strip-like pixel electrodes within the same sub-pixel have a same direction in the figure.
Later, a two domain structure was proposed. In the two domain structure, a sub-pixel can be divided into two parts of left and right, and strip-like pixel electrodes for the two parts are bilaterally symmetric, so that chromatic aberration can be further decreased. However, black vertical stripes occur at the junction of two domains at the center of the sub-pixel.
Later, a pixel structure design was proposed by US Patent Application Publication No. US 2002/0041354, as shown in FIG. 2. The pixel unit also has a two domain structure and is divided into two parts of upper and lower, and strip-like pixel electrodes for the two parts are longitudinally symmetric, so that an effect of low chromatic aberration is obtained, and at the same time, a black-stripe region at the junction of domains is reduced and the transmissive characteristic is enhanced.
However, the forgoing existing technologies did not resolve black stripes at edges of pixels. At an edge of a pixel unit in the ADS mode, due to a disturbed electric field produced by a gate line or a data line and an influence brought by a pixel-electrode edge per se, the electric field direction in this place is inconsistent with direction of the fringe field for driving liquid crystals inside the pixel unit, so that an orientation disorder of liquid crystals occurs at the edge of the pixel unit. A, B shown in FIGS. 1 and 2 are regions of the orientation disorder of liquid crystals in the neighborhood of data lines and gate lines, respectively. Presence of the black stripes will affect transmittance and response speed of the display panel. For improving the display effect, a wider black matrix is usually prepared on an opposed color filter substrate so as to shield the regions of the orientation disorder, which causes degradation of the aperture ratio. Thus, transmittance is reduced.